1. Field of the Invention
This invention relates to an electric contactor suitable to for use in achieving an electrical connection with a lead pin many of which are designed to project downwardly from an electric part such as a pin grid array type IC of high density.
2. Prior Art
Heretofore, in an electric contactor of the type mentioned above, lead pin clamping portions are formed by bending a punched-out plate to form a pair of resilient contact elements arranged in an opposing relation with a very small distance between opposing surfaces of the pair of resilient contact elements. By forming the distance between the clamping portions comparatively small relative to the thickness (diameter) of the lead pin formed of a round pin, many of which highly densely project from a lower surface of the body of an electric part such as an IC, it becomes possible that when the lead pin is introduced between the pair of resilient contact elements, i.e., into the very small gap between the lead pin clamping portions, the pair of resilient contact elements are displaced outwardly against the resiliency thereof and the lead pin is clamped generally on its same circumferential surface by the restoring force of the pair of resilient contact elements, thereby achieving an electric connection.
However, electric parts such as ICs, which have recently become more and more highly integrally formed, are obliged to have smaller lead pins than ever in order to fulfil the requirement for arranging and projecting the lead pins at very small pitches and in high density. Therefore, electric contactors are also required to be made smaller than ever, and this makes it necessary to reduce the small distance between the pair of resilient contact elements (lead pin clamping portions) to the extent possible.
However, in the process for forming such very small electric contactor, there is a limit to the reduction of the distance between the lead pin clamping portions compared with the reduction of the size of the lead pin. Therefore, it frequently happens that the distance between a pair of lead pin clamping portions in one electric contactor is not equal to that of another electric contactor. This naturally results in insufficient reliability in clamping pressure of the lead pin clamping portions.
The conventional electric contactor encounters another inconvenience when a metal plating is applied to an electric contactor after the completion of shaping of the electrical contactor. If the electric contactor, which is to be subjected to metal plating, has lead pin clamping portions which are held in an opposing relation with a very small distance therebetween or which are somehow in abutment relation, there is a fear that an inferior metal plating will result. This eventually leads to an insufficient electrical connection (i.e., lack of reliability) between the contactor and a lead pin of an electric part. With respect to a technique for reducing the distance between the pair of resilient contact elements by means of bending the contactor, there is also a technical limit and it is extremely difficult to manufacture an electric contactor with high precision.